In recent years, an organic EL (electroluminescent) display (OLED display) with an active matrix has been energetically developed. This is because the organic EL display has features such as high-speed response, high contrast, and thin shape.
In a color organic EL display, in order to develop three primary colors of RGB, each pixel formed in a matrix includes a red-displaying pixel displaying R, a green-displaying pixel displaying G, and a blue-displaying pixel displaying B.
Luminous efficiency of a conventional OLED display becomes low because it utilizes luminescence of sub-pixels of R and B, which are not efficient to display frequently appearing pale colors. Moreover, there is a problem for the conventional OLED display with a sub-pixel emitting a white color. Even though luminescence from the W sub-pixel having a high efficiency is utilized to display colors other than the white color, it is necessary to compensate remaining colors with other sub-pixels having a color filter, resulting in a low luminous efficiency for the remaining colors.
Moreover, there is also a problem in which the luminous efficiency decreases with time because it is necessary to increase current flowing in a light emitting layer when having a bright display using a pixel having low luminous efficiency.